1. Field of the Invention
The present invention relates to an air conditioning system which reduces energy consumption by disposing of waste heat to a low temperature heat sink. More particularly, the present invention relates to a system which utilizes existing municipal water supplies or effluent as a water supply for absorption or rejection of heat.
2. Description of the Prior Art
Many residential and commercial air conditioning systems employ conventional heat pumps. Such conventional heat pump systems operate on a closed vapor compression/expansion cycle with heat being rejected to ambient air. Systems of this type include an evaporator with a refrigerant expansion valve, heat exchangers, a directional control valve and suitable fans and auxiliary components. In the conventional heat pump system, the heat exchangers are alternately operated as evaporators and condensers to achieve heating or cooling depending upon the position of the directional control valve in the interconnecting fluid conduit. One heat exchanger unit, the indoor unit, has associated apparatus such as a fan. The other heat exchanger, the outdoor unit, is operated to either add heat to the system or remove heat from the system.
Water source heat pumps (WSHP) are a specialized type of heat pump which are reverse cycle units that use water as a heat source when in the heating mode and as a heat sink in the cooling mode. Thus, heat is absorbed or rejected in a fluid medium rather than in ambient air. Water loop heat pumps (WLHP) use a circulating water loop. When the loop water temperatures exceed a certain level due to the heat added as a result of the heat pump cooling, a device such as a cooling tower dissipates heat from the water loop to the atmosphere. When the water loop temperature drops below a prescribed level due to heat being removed as a result of heating of ambient air at the indoor unit, heat is added to the circulating loop water usually through an auxiliary component such as a boiler.
The water supply may be a recirculating closed loop, well lake or a stream. Reference is also made to the ASRAE 1988 Equipment Handbook, Chapter 43. Various patents can be found in the prior art dealing with water source heat pumps.
U.S. Pat. No. 4,238,933 shows an air conditioning system which reduces energy consumption by disposing of waste heat to a low temperature heat sink and at the same time recovers usable energy. An auxiliary liquid cooled condenser is connected in parallel with the air condenser of a conventional vapor compression air conditioning system across a valve located between the compressor of the existing system and the condensers. When the valve is actuated, the refrigerant of the air conditioning system is directed from the air conditioner, through the liquid cool condenser assembly in heat exchange relationship with the body of fluid which is at lower temperature than ambient air such as water from a swimming pool or from a municipal water supply. Energy conservation is achieved by use of the total heat content of the refrigerant rather than only the high temperature heat as in prior art sources.
U.S. Pat. No. 4,538,418 discloses a water source heat pump system having a fluid refrigerant compressor. The heat pump system further includes first and second heat exchanger units. Suitable fluid conduits interconnect the fluid refrigerant compressor and the heat exchange units in series relationship. A pre-heat exchanger is connected between the water source and the heat exchangers which control the water temperature to the second heat exchanger. In the cooling mode, the water supply will bypass the pre-heat exchanger. Flow control valves are interconnected between the water source and the second heat exchanger unit for controlling the amount of water flowing from the water source to the second heat exchanger. The flow control valves are responsive to the pressure at the outlet of the fluid refrigerant compressor to automatically optimize the operating conditions of the heat pump. The water source may comprise a well, stream or body of water such as an ocean or lake. The water source may also comprise a closed system such as an above-ground or underground water storage tank or underground pipe loop system.
As mentioned above, it is well known in the art that the energy consumption of an air conditioning system may be reduced by use of a low temperature heat sink while at the same time recovering the rejected heat for possible other applications. Other systems which utilize sources such as swimming pool water as a heat sink are shown in U.S. Pat. Nos. 4,019,338; 3,976,123 and 3,926,008.
While the above systems are effective, they differ from the present invention in a number of important aspects, particularly with respect to their application as retrofit systems to existing installations. The present invention relates to a system that is cost-effective as a retrofit to existing air conditioning installations, particularly commercial installations. With the present invention, existing cooling towers which are conventionally used to cool the water loop and which are highly maintenance intensive and have an operational lifetime of only 10 to 20 years, are eliminated. The elimination of the cooling tower not only eliminates the cost of maintenance of a cooling tower but also eliminates the substantial water loss that occurs through use of cooling towers. For example, cooling tower for an air conditioning system for a 40 story, 800,000 square foot building, will utilize about 150,000 gallons of water per day, about one-half of which is discharged to waste or lost through evaporization.
It is also within the scope of the present invention to provide a system which replaces the exterior compressor and condensing coil components of air-to-air split systems common in smaller installations where it is not economical to install water cooling tower systems. In the modified system, a potable water loop is provided to each unit from municipal water supply or other water source. Such a system is more efficient than conventional air-to-air systems and requires only a minimum of modification.